Is Caffeinated Tea Dehydrating?

Is Caffeinated Tea Dehydrating?
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Comparing up to six cups of caffeinated black tea a day to water, researchers study the assertion that tea acts as a diuretic, and is not as hydrating as plain water.

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For years, I’ve recommended that the healthiest beverage to drink is tea—even healthier than water, since tea has all the water of water, yet as a bonus carries a huge load of nutrition without adding calories. But: “There is a belief that caffeinated drinks, such as tea, may adversely affect hydration.” Now this was based on experiments done with high-dose caffeine pills, though, which may not entirely reflect the likely impact of tea, which is a more complex substance.

So, researchers compared four cups of black tea to four cups of water, and six cups of black tea to six cups of water. They kept volunteers locked up for 24 hours, so they could measure every drop going in, and every drop coming out.

The tests revealed no significant differences between tea and water for any of the average blood or urine measurements. It was concluded that black tea, in the amounts studied, offered similar hydrating properties to water. “Thus, tea could be considered a healthy choice of beverage.” And health professionals that don’t know any better and “incorrectly identify tea as a diuretic, could be misleading people and serve to drive consumption towards less healthy beverages.”

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Serena.

Please consider volunteering to help out on the site.

Image thanks to ienjoysushi / flickr

For years, I’ve recommended that the healthiest beverage to drink is tea—even healthier than water, since tea has all the water of water, yet as a bonus carries a huge load of nutrition without adding calories. But: “There is a belief that caffeinated drinks, such as tea, may adversely affect hydration.” Now this was based on experiments done with high-dose caffeine pills, though, which may not entirely reflect the likely impact of tea, which is a more complex substance.

So, researchers compared four cups of black tea to four cups of water, and six cups of black tea to six cups of water. They kept volunteers locked up for 24 hours, so they could measure every drop going in, and every drop coming out.

The tests revealed no significant differences between tea and water for any of the average blood or urine measurements. It was concluded that black tea, in the amounts studied, offered similar hydrating properties to water. “Thus, tea could be considered a healthy choice of beverage.” And health professionals that don’t know any better and “incorrectly identify tea as a diuretic, could be misleading people and serve to drive consumption towards less healthy beverages.”

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Serena.

Please consider volunteering to help out on the site.

Image thanks to ienjoysushi / flickr

Doctor's Note

This is the second video of my four-part video series about the latest discoveries on tea. See Antimutagenic Activity of Green Versus White Tea also. The nutrition without calories concept refers, not surprisingly, to my video Nutrition Without Calories. For more on caffeine myths, see What About the Caffeine? For the antioxidant comparison of black tea to other teas, see Better Than Green Tea? The “less healthy beverages” line is likely an allusion to soda, about which I have a dozen videos, including Food Industry “Funding Effect”Mercury in Corn Syrup?Diet & Hyperactivity; and Is Sodium Benzoate Harmful? 

For more context, check out my associated blog posts: Is Caffeinated Tea Really Dehydrating? and Schoolchildren Should Drink More Water.

If you haven’t yet, you can subscribe to my videos for free by clicking here.

31 responses to “Is Caffeinated Tea Dehydrating?

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  1. This is the second video of a four-part series about the latest discoveries on tea. See yesterday’s NutritionFacts.org video-of-the-day Antimutagenic Activity of Green Versus White Tea also. The nutrition without calories concept refers, not surprisingly, to my video Nutrition Without Calories. For more on caffeine myths see What About the Caffeine? For the antioxidant comparison of black tea to other teas, see Better Than Green Tea?. The “less healthy beverages” line is likely an allusion to soda, about which I have a dozen videos, including Food Industry “Funding Effect”, Mercury in Corn Syrup?, Diet & Hyperactivity, and Is Sodium Benzoate Harmful?. Then there are 1,363 other topics to explore!




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        1. I’ll dot my I’s, but don’t cross my T’s, ’cause. . .

          Hot or cold,
          White, Black or Gold
          Anytime is the right time
          For ‘T’ea time.




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    1. Adrenal exhaustion?
      I thought caffeine consumption causes the adrenal glands to produce epinephrine, norepinephrine, cortisol which eventually wears them out as well as causing other high-blood pressure related problems.

      Long-term negative effects on the brain?
      Dr. Daniel Amen M.D., brain expert and founder of Amen Clinics recommends quitting coffee/tea because of negative long-term effects on the brain.

      Appreciate your hard work and advice.




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  2. There are probably more properties to tea, as with any food. Since you like alma & triphala, perhaps you’ve started to believe that people can observe effects merely thru observation. Before the Christian shame of the body, medicine was much different, since people were more observant, and they attributed many things to food, like the effect on the humors. Best would be to read the original ancient texts from Greece, Rome, China, India, Egypt, Persia, Babylon… and then try to confirm their observations thru ‘modern’ studies.

    Not sure if correct, but here’s something from Chinese Nutrition Therapy.Thermal nature – Green & white: cold, Black: cool to slightly warmingFlavor – Bitter and sweetOrgan network – Stomach, lunch, heart, kidneysPhase – Wood, earth, fire (not clear)Effect – Clears heat, especially in head region; quenches thirst, diuretic, downbears qi, disperses digestive obstruction, refreshes the mind, transforms phlegm and dampness, detoxifies, harmonizes stomach (black tea)IndicationsWind-cold disorders – Aching, itchy eyes: blurred vision, headaches, heat sensation and dizziness in head
    Summer heat with strong thirst
    Heat symptoms – Thirst, nervousess, agitation after excessive alcohol consumption
    Damp-heat disorders – Diarrhea or dysenteryDamp-heat – Fatigue, exhaustion, heavy extremities
    Heat symptoms – Agitation, nervousness, after excessive alcohol consumptionInternal wind-heat – Sensation of heat in head, dizziness, blurred vision, headaches and aching eyesContraindicationsCold and vacuity of stomach and spleenSleep disturbancesExcess dries out body fluids, especially blood (xue). Exercise caution with blood vacuity.




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    1. “Best would be to read the original ancient texts from Greece, Rome, China, India, Egypt, Persia, Babylon… and then try to confirm their observations thru ‘modern’ studies.”  Okay, I just did my first study based on your methodology.  I asked both menstruating and non-menstruating women to touch various flowers.  None of them could kill/wilt the flower just by touching it, contrary to what’s described in the annals of your medical “sources.”




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  3. I had heard this about green and white teas but not black — interesting! I believe, as well, that, just personal observation infidates this, too. I know lots of iced tea drinkers (black teas) that guzzle it during the hot summer months and don’t notice dehydration. I’m not a big black-tea drinker, but was in the past. Good to know that if I do drink it I won’t shrivel up :^)




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  4. Yay! This is great news. I’m a big fan of black tea, hot or cold, but I always worried that I was sabotaging my need for fluids, especially on hot days.  Tea time, anyone?




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      1.  My recipe for quick-n-simple iced tea:
            heat-proof tall glass
           1 teabag of your choice (I prefer black tea)
            boiling water
        Put the teabag in the glass, pour in just enough boiling water to cover the teabag. Let it steep 3-5 minutes, remove the teabag and add cold water and LOTS of ice.
        For a classy touch add a sprig of fresh mint or a wedge of lemon.
        Enjoy!




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        1. Actually, because you only add enough hot water to cover the tea bag, you’re not extracting as much from the tea as you would by adding a full cup of hot water.  It has to do with the saturation point of the solute in the solvent.  The solute reaches its saturation point much faster in a solution which includes less solvent (water, in your case).  Try it yourself; see how much salt you can fully dissolve (dissociate) in one tablespoon of water.  Then add a cup of water to it, and try again.  That’s in essence what you’re doing with the tea  antioxidants… never letting them dissolve to their greatest potential.




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          1.  Hi Lew,
            Thnx for the info!
            From now on I’ll add a full amount of hot water and let the teabag steep long enough for the antioxidants to dissolve properly.




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  5. Ok, Black tea is not a diuretic but what about the affects of the caffeine?  Doesn’t a caffeine buzz affect health?  Wouldn’t one be jittery with 6 cups of black tea?  Is this discussed elsewhere?




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  6. I’m very pleased to see my research discussed – thanks for that. The health effects of caffeine were reviewed in another of my papers which found that intakes up to 400mg per day were not associated with negative health effects. That equates to 8 cups of tea or 4 cups of coffee, on average. The reference is Ruxton, CHS (2008).  The impact of caffeine on mood, cognitive function,
    performance and hydration: a review of benefits and risks. Nutrition Bulletin, 33, 15-25.




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  7. Dr.G,I would guess that coffee would yield about the same results as tea.Any “thots”? P.S. when it says to “read more”,it always takes me to your video(which is always edifying);is there an easy way to get the origianal articles?  Dr.J  




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  8. Dr G,

    This would also apply to moderate coffee intake also, right?  (Assuming black coffee)  Can’t quite get the missus from coffee to white tea :)




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  9. I’m delighted to finally see an actual study on whether tea is dehydrating and an going to share this video with my readers. It’s too bad that all caffeinated drinks get lumped together as bad when there is no comparison between drinking green tea and Mountain Dew!
    Green tea also contains theanine which has relaxing properties that may counter the effects of caffeine. I drink a lot of iced green tea and it never makes me jittery like coffee does. I’d love to know your thoughts on whether this is true?




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  10. Hi Dr. G. I recently
    came across a tea called guayusa that is touting some great health
    benefits (twice the antioxidants of green tea?) but was curious as to
    your thoughts on the product since it still contains a great deal of
    caffeine. I searched your site to no avail, no info on guayusa but I
    would love to hear your thoughts!




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  11. Tea leaves are roasted, some kinds more than others. Drinking tea made with roasted tea leaves has a drying effect, which is not the same thing as being dehydrated.




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    1. In fact, there is an article and/or video on this website that says that women (I believe they used women as the example) who drank green tea had better skin hydration.




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